In the prior art, a known type of such glass substrate for a magnetic recording medium is described in, for example, Japanese Laid-Open Patent Publication No. 2002-32909. The glass substrate described in this publication includes concentric pits and lands formed on a main surface. The height of the pits and lands is of a size that does not have anisotropy in a circumferential direction when at least a magnetic film is formed on the substrate. In other words, a magnetic anisotropy value expressed by a ratio (Hc1/Hc2) of coercive forces, where the coercive force in the circumferential direction is Hc1 and the coercive force in a radial direction is Hc2. The ratio is set in a range of 0.90 and 1.10.
However, in the glass substrate having a texture with a small magnetic anisotropy in which the ratio of the coercive forces is between 0.90 and 1.10, the levitation stability of a magnetic head for reading information from the glass substrate cannot be realized, and low levitation characteristic is insufficient. For the low levitation characteristic, in addition to a limit levitation characteristic (e.g., TDH), properties associated with the durability and levitation stability of the magnetic head which are evaluated in a continuous seek test or a fixed point levitation test are essential. Satisfactory low levitation characteristic is obtained only when such properties are satisfied. TDH is the abbreviation for Touch Down Height and is the levitation amount of the head when the levitation amount of the head is sequentially lowered and the head begins to contact the magnetic disk.
The present invention was made in view of the above problems existing in the prior art. It is an object of the present invention to provide a glass substrate for a magnetic recording medium that lowers the levitation amount of the magnetic head and improves the levitation stability, and to a method for manufacturing the same.